I've never tried a liquid vitamin, so I can't vouch for flavor or efficiency. I noticed that Drugstore.com sells a berry flavor liquid vitamin, though it's geared towards seniors. Have you considered a chewable children's vitamin, such as Flintstones? My 43 year old sister takes those
She also can't do pills.
The best source of liquid calcium is milk
I read an article just today, about how teenagers don't drink enough milk. Aside from that, a good source would be the chocolate calcium supplements like Viactiv. They come in other flavors, too, and are very good.